<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>

        class Person {
            static num = 0
            // static num = null
            constructor(name) {
                // if (!Person.num) {
                //     Person.num = this
                // } else {
                //     return Person.num
                // }
                Person.num++
                this.name = name
            }
        }
        let zhangsan = new Person("张山")
        let lisi = new Person("李四")
        console.log(zhangsan, lisi)
        console.log(Person.num)
    </script>
</body>

</html>